Define nitrogen estimation - kjeldahl''s method, Biology

Assignment Help:

Define Nitrogen Estimation - Kjeldahl's Method?

Nitrogen in the protein is estimated by a method referred to as Kjeldahl's method. Although over a period of time many other methods have emerged for determination of organic nitrogen, this method still remains an old favourite because it is reliable and has very well standardized procedures. The method involves the digestion of the weighed sample with concentrated sulphuric acid, selenium oxide, potassuim sulphate and copper sulphate in a long necked special digestion flask known as kjeldahl's flask. Potassium sulphate increases the boiling point of the mixture. Since the digestion results in fuming of the sulphuric acid, the procedure has to be carried out in a fume hood and the procedure takes several hours. The sample is digested until the solution in the digestion flask becomes clear after which it is transferred to an appropriate volumetric flask (usually 50 or 100 ml flask) and the volume is made up to the mark with distilled water. Aliquots of this sample are used for distillation in the kjeldahl's apparatus and nitrogen in the protein is estimated. Most proteins contains 16% nitrogen. Thus, percent nitrogen content is multiplied by 6.25 to get crude protein content.

1805_Nitrogen Estimation - Kjeldahl’s Method.png

The experiment involves decomposition of ammonium sulphate by a fixed volume of alkali (NaOH). Ammonium sulphate on decomposition releases ammonia which is collected in a flask of boric acid solution Tashiro's indicator. With boric acid ammonia forms a complex 'ammoium borate'. As ammonia is distilled into the boric acid, the Tashiro indicator slowly changes colour from pink to green. This is because the colour of the indicator is pH dependent - it is pink in acidic medium and green in alkaline medium. When the green coloured solution containing the boric-acid-ammonia complex is retitrated against H2SO4, the solution slowly becomes acidic again and the indicator becomes pink. This point when colour changes from green to pink is taken as the end point.


Related Discussions:- Define nitrogen estimation - kjeldahl''s method

Muscular force, 2.?In order to increase muscular force production, muscular...

2.?In order to increase muscular force production, muscular contractions may be modulated in two ways. Explain.

What do you mean by oxalates, Q. What do you mean by Oxalates? Oxalates...

Q. What do you mean by Oxalates? Oxalates are widely distributed in plant foods mostly in the form of calcium salts. Oxalates are known to interfere with calcium absorpti

What is the probability of two individuals, What is the probability of two ...

What is the probability of two individuals (AaBBccDd and aaBbCcDd) having a child with the following genotype AaBBCcDD?

Explain re- pera at ions and other interventions, Explain Re- pera at ions ...

Explain Re- pera at ions and Other Interventions ? These are required for residual VSD with significant shunt, residual RV obstruction and pulmonary valve regurgitation in a fe

Chronic aortic regurgitation-types of regurgitation, Chronic Aortic Regurgi...

Chronic Aortic Regurgitation :  The aetiological factors leading to aortic regurgitation are: (1) rheumatic, (2) annulo aortic ectasia, (3) native valve endocarditis, (4) c

What is pollination, What is pollination? What are the main forms of pollin...

What is pollination? What are the main forms of pollination? The process in which pollen grains (the male gametophytes of phanerogamic plants) reach the female gametophyte is k

Kreb cycle assignment, I want to do assignment on kerb cycle with in text c...

I want to do assignment on kerb cycle with in text citation

Study of embryology, Embryology This is the study of growth, fertilizatio...

Embryology This is the study of growth, fertilization, division or differential of the zygote into embryo of early development of living beings before the attainment of structure

What is the role of pharmacologic therapy, What is the role of pharmacologi...

What is the role of pharmacologic therapy in the treatment of peri implantitis. Pharmacological therapy for patients presenting with an ailing implant involves subgingival irri

Explain about the hypokalemia, Explain about the Hypokalemia? Normal s...

Explain about the Hypokalemia? Normal serum K ranges from 3.5-5 mM/L. Hypokalemia or low plasma K levels can occur with a net shift of K from the plasma to the cells. This shi

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd